The present invention relates to a so-called pilgrim step rolling which is a method using basically a reciprocating roll stand for advancing and reducing the item being. More particularly the invention relates to advancing and rotating rolls used for the pilgrim step rolling of tubes, rods or the like; a cold rolling method is being preferred. The rolled stock is either turned or advanced or both in a dead center of the path of reciprocation of the roll stand.
The pilgrim step cold rolling method and equipment is known wherein generally, during rolling, the frame and roll mount reciprocates. The stock e.g. a tube or pipe is turned and/or advanced in one or both dead center positions of the reciprocating frame. Thus during most of the rolling procedure the stock is basically at rest vis-a-vis the frame as well as in relation to roll axes. The known methods are disadvantageous in that the torque required for turning the stock is to be developed within a short period of time. These acceleration moments set limits for the power performance of the cold rolling pilgrim step method.
In order to obviate these drawbacks, methods and equipment have been suggested to eliminate the acceleration and to provide for rotation of the stock as well as for advancing it at a constant rate. Unfortunately these methods are usable to a limited extent only since a part of the rotation of the rolled stock which occurs in between period of engagement of the rolled stock itself and the rolls, is stored elastic energy. This storage of elastic energy when released does produce a torque. However this torque has to be developed and applied basically by friction between the rolled stock and the clamping elements which are provided for holding that stock. The situation is quite similar as far as advance is concerned. In case the advance is rapid, there is a particular limit given by the elastic properties of the advancing equipment on one hand and the rolls in conjunction with the mandrel on the other hand.